Pages

Search PPTs

Thursday, July 25, 2013

2.RAMA RAM constitutes the internal memory of the CPU for storing data, program and program result. It is read/write memory. It is called random access memory (RAM).Since access time in RAM is independent of the address to the word that is, each storage location inside the memory is as easy to reach as other location & takes the same amount of time. We can reach into the memory at random & extremely fast but can also be quite expensive.

3.RAM is volatile, i.e. data stored in it is lost when we switch off the computer or if there is a power failure. Hence a backup uninterruptible power system(UPS) is often used with computers. RAM is small , both in terms of its physical size and in the amount of data it can hold.

4.There is two type of RAM:-

Static RAM (SRAM)Dynamic RAM (DRAM)

5.RAM

6.Static RAM (SRAM)The word static indicates that the memory retains its contents as long as power remains applied. However, data is lost when the power gets down due to volatile nature. SRAM chips use a matrix of 6-transistors and no capacitors. Transistors do not require power to prevent leakage, so SRAM need not have to be refreshed on a regular basis.

7.Because of the extra space in the matrix, SRAM uses more chips than DRAM for the same amount of storage space, thus making the manufacturing costs higher.Static RAM is used as cache memory needs to be very fast and small.

8.Characteristic of the Static RAMIt has long data lifetimeThere is no need to refreshFasterUsed as cache memoryLarge sizeExpensiveHigh power consumption

9.Dynamic RAM (DRAM)DRAM,unlike SRAM, must be continually refreshed in order for it to maintain the data. This is done by placing the memory on a refresh circuit that rewrites the data several hundred times per second. DRAM is used for most system memory because it is cheap and small. All DRAMs are made up of memory cells. These cells are composed of one capacitor and one transistor.

10.Characteristic of the Dynamic RAMIt has short data lifetimeNeed to refresh continuouslySlower as compared to SRAMUsed as RAMlesser in sizeLess expensiveLess power consumption